The invention relates to a monitoring device for monitoring the function of a reporting system, the reporting system comprising a plurality of reporting devices and/or signalling devices, supply lines, and a voltage source, wherein the reporting devices and/or signalling devices are connected to the voltage source via the supply lines, and the reporting devices and/or signalling devices are connected in parallel to one another and to the voltage source. The invention furthermore relates to a reporting system comprising this monitoring device, and a method for checking the operating capability of a or the reporting system.
Reporting systems, such as fire alarm systems, alarm systems, or the like, are used as communication devices usually in large plants, wherein reports are generated automatically or manually at decentralized locations, and are forwarded to a control center. To this end, the reporting systems comprise a plurality of reporting devices which are connected to each other and the control center via signal lines and/or supply lines. According to a widespread embodiment, the supply lines and signal lines are combined to form a two-wire line, wherein the change in current flow or voltage is monitored in the two-wire line and, if changes are detected, a report is generated in the control center.
Publication DE 10 2005 038 602 A1, which is the closest prior art, describes, in the introduction, a safety device of that type that uses d.c. line technology, wherein the safety device includes primary lines in the form of circuits supplied with direct voltage, at the end of which, i.e. at the point to be monitored, a terminal resistor is disposed. The terminal resistor and the current flow through this terminal resistor are monitored by an evaluation circuit in the control center. If the resistance value of the terminal resistor changes e.g. by more than plus/minus 40%, this is interpreted as external intervention, and an alarm is triggered.